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Title: Tracing sediment movement on semi-arid watershed using Rare Earth Elements 1988

item Nearing, Mark
item Nichols, Mary

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2009
Publication Date: 7/1/2009
Citation: Polyakov, V., Kimoto, A., Nearing, M.A., Nichols, M.H. 2009. Tracing sediment movement on semi-arid watershed using Rare Earth Elements. Soil Science Society of America Journal. 73:1559-1565.

Interpretive Summary: This study uses a new technique to look at spatial patterns of soil erosion and sediment movement on a semi-arid rangeland watershed. There is currently very few data on the processes by which sediment moves around on semi-arid hillslopes. This new technique involves the use of rare earth element oxides, which are tagged to surfaces of the watershed and subsequently tracked as the soil moves through the watershed to the outlet. The data are unique. While we have long been able to measure the total amount of sediment generated by erosion on a tract of land, no previous studies have allowed us to quantify the relative amounts emanating from specific portions of the watershed. The new data will be useful in terms of developing and testing models of erosion, as well as showing that the new technique is useful in the rangeland environment. The study results enable improved understanding of water erosion on rangelands in the western U.S.

Technical Abstract: A multi-tracer method employing rare earth elements (REE) was used to determine sediment yield and to track sediment movement in a small semiarid watershed. A 0.33 ha watershed near Tombstone, AZ was divided into five morphological units, each tagged with one of five REE oxides. Relative contribution of each unit to the total sediment yield was determined by collecting runoff and sediment, and the spatial redistribution of sediment was determined from sampling the soil surface. Average sediment yield was 1.0 t ha-1 y-1 from the entire watershed, but varied between 0.1 t ha-1 y-1 from the upper slope to 5.0 t ha-1 y-1 from the lower channel. Little re-deposition occurred in the channels indicating an effective transport system. The erosion pattern and rates were in agreement with the current morphology of the watershed, which has a well developed channel network.